The purpose of this repeated dose study is to develop recommended dosing information for initiation of therapy with OROS Hydromorphone in patients with chronic non-malignant pain converting from other strong oral or transdermal opioids. It will also assist in the development of a recommended starting dose by which patients can be titrated to an appropriate maintenance dose of OROS Hydromorphone HCI. The safety profile for OROS Hydromorphone HCI will also be evaluated.